I bought an usb to serial converter module with FT232RL chip on it. it was working fine and then with my mistake the chip went down.

then I replace it with a new FT232RL chip. since that time the module just works for the first time ( I use it to program a headerboard of ARM lpc2138) and then it doesn't work. and all other usb ports stops working too..

It sounds like you broke the hub. Have you gone through normal checks -shut down the computer and removing the power from all peripherals then restoring power and rebooting?

If you reboot without your serial adapter but the USB ports still don't work, the hub (possibly a root hub in your computer) is probably broken. Remembering that this is a computer, there probably a lot of other things that can cause the symptom you mentioned, but a dead hub sounds the lost likely from what you have posted.

when this happen I want to restart or shutdown the laptop but it does not!! then I have to remove the battery to force it to shut down. but then when I restart the pc the usb ports works correctly until I use the converter again..

It could be that some short was made on the board then you replaced the FTDI chip. Then you use the converter. Some sort a short circuit protection kicks in on your laptop USB hub system. The protection is reset then after a power up. And then all works as normal